Automated transfer of a data unit comprising a plurality of fundamental data units between a host device and a storage medium

ABSTRACT

Systems and methods for transferring data between a host device and a storage medium are provided. In one implementation, a method for transferring data between a host device and a storage medium includes receiving from the host device a command to transfer data between the host device and a storage medium, storing in a first register a value that is correlated to a number of second data units contained in a first data unit, and storing in a second register a value for tracking a number of second data units that are transferred between the host device and a buffer.

FIELD OF THE INVENTION

[0001] The present invention relates to data transfers between a hostdevice and a storage medium.

BACKGROUND OF THE INVENTION

[0002] Memory controllers are used for transferring data between a hostdevice and a non-volatile semiconductor memory device. A single datatransfer cycle between the host device and the memory device is referredto as a data phase. The completion of a host device's request totransfer data may involve multiple data phases. The completion of a dataphase requires a memory controller to perform actions that are inaccordance with a host interface protocol. Some host interface protocolsallow the exchange of data using data phases comprising relatively largedata units (e.g., blocks) that are multiples of the basic fundamentaldata unit (e.g., sector) used by the memory device for storing data. Theimplementation of a data phase comprising these relatively larger dataunits has traditionally required intervention of the controllermicroprocessor after the transfer of each fundamental unit contained ina larger data unit. Since each read or write operation may comprise alarge number of fundamental units, such read or write operation mayrequire a large number of microprocessor interventions. A large numberof microprocessor interventions is time consuming and can thereforeincrease the time needed to complete a read or write operation inconnection with the memory device. This problem may be alleviated byemploying a faster microprocessor. Such solution, however, may not bevery cost effective. Therefore there exists a need for systems andmethods for solving these and other problems associated withtransferring data between a host and device and a memory device.

SUMMARY

[0003] The present invention relates to systems and methods fortransferring data between a host device and a storage medium. In thisregard, an embodiment of one such method includes receiving from thehost device a command to transfer data between the host device and astorage medium, storing in a first register a value that is correlatedto a number of second data units contained in a first data unit, andstoring in a second register a value for tracking a number of seconddata units that are transferred between the host device and a buffer.

[0004] An embodiment of a system for transferring data between a hostdevice and a storage medium includes a host interface that receives fromthe host device a command to transfer data between the host device and astorage medium, a buffer that temporarily stores data that istransferred between the host device and the storage medium, a firstregister that stores a value that is correlated to a number of seconddata units contained in a first data unit, and a second register thatstores a value for tracking a number of second data units that aretransferred between the host device and the buffer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The present invention, as defined in the claims, can be betterunderstood with reference to the following drawings. The drawings arenot necessarily to scale, emphasis instead being placed on clearlyillustrating the principles of the present invention.

[0006]FIG. 1 is a block diagram of a computer network 100 in accordancewith one embodiment of the present invention.

[0007]FIG. 2 is a block diagram depicting an embodiment of the datatransfer system depicted in FIG. 1.

[0008]FIG. 3 is a flow chart depicting a method that may be implementedby the data transfer system depicted in FIG. 2.

[0009]FIG. 4 is a block diagram depicting an embodiment of the hostinterface of the data transfer system depicted in FIG. 2.

[0010]FIG. 5 is a block diagram depicting an embodiment of the datamover of the data transfer system depicted in FIG. 2.

[0011]FIG. 6 is a block diagram depicting an embodiment of the storagemedium interface of the data transfer system depicted in FIG. 2.

[0012]FIGS. 7A, 7B, and 7C are flow charts depicting a non-limitingexample of a method for writing data to the storage medium depicted inFIG. 1 in accordance with an embodiment of the present invention.

[0013]FIGS. 8A, 8B, and 8C are flow charts depicting a non-limitingexample of a method for reading data from the storage medium depicted inFIG. 1 in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

[0014]FIG. 1 is a block diagram of a computer network 100 in accordancewith one embodiment of the present invention. The computer network 100comprises a host 102 and a storage medium (SM) 104 that are coupled to adata transfer system (DTS) 200. In an alternative embodiment, theStorage Medium 104 and/or the Data Transfer System 200 may be part ofthe host 102. The Data Transfer System 200 facilitates read and writedata transfers between the host 102 and the Storage Medium 104. Forexample, in a write operation, data is transferred from the host 102 tothe Storage Medium 104 via the Data Transfer System 200. Similarly, in aread operation, data is transferred from the Storage Medium 104 to thehost 102 via the Data Transfer System 200. The host 102 is a dataprocessing system such as, for example, a desktop computer, a notebookcomputer, a personal digital assistant (PDA), or a mainframe computer,among others. The Storage Medium 104 is preferably a non-volatilesemiconductor memory device such as, for example, flash memory,non-volatile random access memory (non-volatile RAM), or electricallyerasable programmable read only memory (EEPROM), among others.

[0015]FIG. 2 is a block diagram depicting one embodiment of the DataTransfer System 200 (FIG. 1). The Data Transfer System 200 includes adata mover (DM) module 500, a host interface (HI) module 400, a storagemedium interface (SMI) module 600, a buffer 205 (preferably a circularbuffer), a microprocessor 201, memory 202, and a bus 204. As indicatedin FIG. 2, the components of the Data Transfer System 200 may be coupledas follows: the Data Mover 500 is coupled to the Host Interface 400 andto the Storage Medium Interface 600; the Host Interface 400 is coupledto a host 102 (FIG. 1); the Storage Medium Interface 600 is coupled to aStorage Medium 104 (FIG. 1); the microprocessor 201 is coupled to thememory 202; and the Host Interface 400, the Data Mover 500, and theStorage Medium Interface 600 are coupled to the microprocessor 201 viathe bus 204. The Data Mover 500 organizes and controls the flow of databetween the host 102 and the Storage Medium 104. The buffer 205 is usedto buffer data being transferred between the host 102 and the StorageMedium 104. The memory 202 is used for storing a data transfer program203 that is executed by a microprocessor 201 to control the operation ofthe Host Interface 400, the Data Mover 500, and the Storage MediumInterface 600. In a preferred embodiment, the memory 202 comprisesrandom access memory (RAM) and read only memory (ROM), and the datatransfer program 203 comprises firmware. The buffer 205, the HostInterface 400, the Data Mover 500, the Storage Medium Interface 600, themicroprocessor 201, the memory 202, and the bus 204 are preferably, butnot necessarily, part of a single application specific integratedcircuit (ASIC).

[0016]FIG. 3 depicts a flow chart that illustrates a method 300 that maybe implemented by the Data Transfer System 200 (FIG. 2) in accordancewith one embodiment of the invention. In step 301, the Data TransferSystem 200 receives a read or write command from the host 102 (FIG. 1)requesting a read or write operation, respectively. In response toreceiving the command, the microprocessor 201 (FIG. 2) loads registersin the Host Interface 400, the Data Mover 500, and the Storage MediumInterface 600 (FIG. 2) for executing the read or write operationrequested by the command. In a read operation, data is transferred fromthe Storage Medium 104 (FIG. 1) to the host 102. During a writeoperation, data is transferred from the host 102 to the Storage Medium104. After the registers are loaded in step 302, a data unit (e.g., ablock or a sector of data) is transferred between the Data TransferSystem 200 and the host 102 or the Storage Medium 104, as indicated instep 303. The data transfer is coordinated and managed by the HostInterface 400, the Data Mover 500, and/or the Storage Medium Interface600. Data that is transferred between the host 102 and the StorageMedium 104 is buffered in the buffer 205 of the Data Transfer System200. In one implementation of the method 300, a data unit that istransferred between the buffer 205 and the host 102 is a block of datathat may comprise multiple sectors, whereas a data unit that istransferred between the buffer 205 and the storage medium 104 is asector (e.g. 512 bytes). Data is preferably transferred between the DataTransfer System 200 and the host 102 in units of bytes (8 bits) or words(16 bits), and between the Data Transfer System 200 and the storagemedium 104 in units of bytes. After each unit of data is transferredbetween the Data Transfer System 200 and the host 102 or the StorageMedium 104, registers in the Host Interface 400, the Data Mover 500,and/or the Storage Medium Interface 600 are updated in step 304 toreflect the occurrence of the data transfer. After the registers areupdated, a determination is made by the data mover 500 in step 305 as towhether the entire read or write operation requested by the read orwrite command, respectively, is complete. If the entire read or writeoperation is complete, then the microprocessor 201 is interrupted instep 306, and the method 300 terminates in step 307. If, however, theread or write operation is not complete, then the method 300 repeatssteps 303-305 until the read or write operation is complete.

[0017]FIG. 4 is a block diagram illustrating selected components of theHost Interface 400 of the Data Transfer System 200 (FIG. 2) inaccordance with one embodiment of the present invention. The HostInterface 400 interfaces with the host 102 (FIG. 1) and facilitates datatransfers between the host 102 and the buffer 205 (FIG. 2). The HostInterface 400 and the Data Mover 500 (FIG. 5) transmit signals to eachother in order to indicate their respective status and their readinessto perform a certain step. For instance, an H_XferBlk signal 403 fromthe Data Mover 500 to the Host Interface 400 indicates that the buffer205 is ready to provide or receive data to/from the host 102. On theother hand, an H_BlkXferred signal 404 from the Host Interface 400 tothe Data Mover 500 indicates that a block of data has been transferredbetween the buffer 205 and the host 102.

[0018] The Host Interface 400 includes a WordsPerBlk register 401 thatis loaded at the beginning of a read or write operation with the numberof words per block of data. A WordCtr register 402 is used for countingdown the number of words transferred during each block transfer. Priorto each block transfer, the WordCtr register 402 is loaded by receivinga value contained in the WordsPerBlk register 401. In an alternativeembodiment, the WordsPerBlk register 401 is loaded with the number oflongwords per block of data, and the WordCtr register 402 is used forcounting down the number of longwords transferred during each blocktransfer.

[0019]FIG. 5 is a block diagram depicting selected components of theData Mover 500 in accordance with one embodiment of the presentinvention. The Data Mover 500 includes registers containing informationas described in the following table: TABLE 1 Registers that may beincluded in the Data Mover 500 REGISTER NAME CONTENT/DESCRIPTIONHost_LW_Ptr 511 Data buffer 205 long word address for transfers to/fromhost 102 Host_LW_Ctr 513 Long word counter for transfers to/from host102 Host_LW_PerBlk 506 The number of long words per block of dataHostXferSectCtr Counts number of sectors to be transferred (HXSC) 502to/from host 102 SectsPerBlk (SPB) 504 Number of sectors per block ofdata SOB_LW_Ptr 515 Start address of buffer 205 EOB_LW_Ptr 516 Endaddress of buffer 205 SMI_LW_Ptr 512 Data buffer 205 long word addressfor transfers to/from Storage Medium 104 SMI_LW_Ctr 514 Long wordcounter for transfers to/from Storage Medium 104 SMI_LW_PerSect 507 Thenumber of long words per sector. BuffSects 505 Number of sectors in thebuffer 205 MaxBuffSects 510 Size of the buffer 205 DeviceXferSectCtrCounts number of sectors to be transferred (DXSC) 503 to/from StorageMedium 104

[0020] The registers identified in Table 1 are used by the Data Mover500 to manage the transfer of data between the host 102 and the StorageMedium 104. A data transfer between the host 102 and the Storage Medium104 is initiated in response to the Host Interface 400 receiving a reador write command from the host 102. After the Host Interface 400receives a read or write command from the host 102, the Host Interface400 interrupts the microprocessor 201 which loads certain registers ofthe modules Host Interface 400, Data Mover 500, and Storage MediumInterface 600 and then activates them (the modules 400, 500, and 600).After being activated, the Data Mover 500 sends a request for a block ofdata to the Host Interface 400 (for a write operation) or a request fora sector of data to the Storage Medium Interface 600 (for a readoperation). A request for a block from the Host Interface 400 isachieved by sending an H_XferBlk 403 signal to the Host Interface 400,whereas a request for a sector from the Storage Medium Interface 600 isachieved by sending an SMI_XferSect 508 signal to the Storage MediumInterface 600.

[0021] For a read operation, if there is room in the data transferbuffer 205 and if the value of DXSC 503 is greater than 0, then the DataMover 500 requests that a sector of data be transmitted from the StorageMedium 104 to the buffer 205. The Data Mover 500 performs this requestby sending an SMI_XferSect 508 signal to the Storage Medium Interface600. The Data Mover 500 also tracks the progress of the sector transferby managing the DXSC 503, which the Data Mover 500 decrements by 1 aftereach successful sector transfer from the Storage Medium 104 to thebuffer 205. Eventually the DXSC 503 will go to 0, and the Data Mover 500will stop transmitting data transfer requests to the Storage MediumInterface 600. Similarly, for a write operation, as long as there isroom in the data transfer buffer 205 and the value of HXSC is greaterthan the value of SPB 504, the Data Mover 500 hardware will continue torequest that a block of data be transmitted from the host 102 to thebuffer 205 by sending an H_XferBlk signal to the Host Interface 400. TheData Mover 500 will also track the progress of the transfer by managingthe HXSC 502, which is decremented by the value of SPB after eachsuccessful block transfer from the host 102 to the buffer 205.Eventually the HXSC 502 will go to 0, and the Data Mover 500 will stoptransmitting data transfer requests to the Host Interface 400.

[0022] Data transfers between the data transfer buffer 205 and the HostInterface 400 or Storage Medium Interface 600 are preferably in units oflongwords (e.g., 4 bytes). As each longword is transferred, Data Mover500 hardware decrements either the Host_LW_Ctr 513 or the SMI_LW_Ctr 514depending on whether the transfer is to/from the host 102 or the StorageMedium 104. In addition, word counters internal to the Host Interface400 and Storage Medium Interface 600 are decremented. At the end of asector transfer to/from the Storage Medium 104, the Storage MediumInterface 600's internal word counter goes to 0, prompting it to sendthe sector acknowledgment SMI_SectXferred 509 to the Data Mover 500,which is expecting this signal because its own SMI_LW_Ctr 514 has goneto 0. If there are more sectors to be transferred (i.e., if the value ofDXSC 503 is greater than 0), then upon receipt of the SMI_SectXferred509 signal, the Data Mover 500 hardware reloads the SMI_LW_Ctr 514 fromthe register SMI_LW_PerSect 507 and issues another SMI_XferSect 508signal to the Storage Medium Interface 600. Similarly, at the end of ablock transfer to/from the host 102, the internal word counter WordCtr402 of the Host Interface 400 goes to 0, prompting the Host Interface400 to send the block acknowledgment Host_BlkXferred 404 to the DataMover 500 which is expecting this signal because its Host_LW_Ctr 513 hasalso gone to 0. If there are more blocks to be transferred, then uponreceipt of the Host_BlkXferred 404 signal, the Data Mover 500 hardwarereloads the Host_LW_Ctr 513 from the register Host_LW_PerBlk 506 andissues another Host_XferBlk 403 signal to the Host Interface 400.

[0023]FIG. 6 is a block diagram illustrating selected components of theStorage Medium Interface 600 of the Data Transfer System 200 (FIG. 2) inaccordance with one embodiment of the present invention. The StorageMedium Interface 600 interfaces with Storage Medium 104 (FIG. 1) andtransfers data between the buffer 205 (FIG. 2) and the Storage Medium104 in response to receiving an SMI_XferSect signal 508 from the DataMover 500. After the Storage Medium Interface 600 transfers a sector ofdata between the buffer 205 and the Storage Medium 104, it transmits anSMI_SectXferred signal 509 to the Data Mover 500 confirming the datatransfer. Registers contained in the Storage Medium Interface 600include an SMI_XferLen register 601 that indicates the number of datasectors to be transferred and an SMI_XferCtr register 602 that countsdown the number of sectors transferred. The SMI_XferCtr register 602 isloaded with the value contained in the SMI_XferLen register 601 prior toeach read or write operation.

[0024] With additional reference to FIG. 5 throughout the remainingfigure descriptions, FIGS. 7A, 7B, and 7C are flow charts depicting anon-limiting example of a write method that is performed by the DataTransfer System 200 (FIG. 2) in accordance with one embodiment of thepresent invention. In step 701, the Host Interface 400 (FIG. 2) receivesa write command from a host 102 (FIG. 1). In response to receiving thewrite command, the Host Interface 400 interrupts the Microprocessor 201(FIG. 2) which, in step 702, loads the number of sectors per block intoSectsPerBlk (SPB 504), the transfer length in sectors intoHostXferSectCtr (HXSC 502) and DeviceXferSectCtr (DXSC 503), the numberof longwords in a sector into SMI_LW_PerSect 507, and the number oflongwords in a block into Host_LW_PerBlk 506. In addition, theMicroprocessor 201 sets BuffSects 505 to MaxBuffSects 510, setsHost_LW_Ptr 511 and SMI_LW_Ptr 512 to SOB_LW_Ptr 515, and then activatesthe modules Host Interface 400, Data Mover 500, and Storage MediumInterface 600 (FIG. 2).

[0025] Subsequently, in step 703, the Data Mover 500 determines if theamount of data remaining to be transferred is less than a block's worthof data; this determination is based on whether the value of HXSC 502 isless than the value of SPB 504. If the value of HXSC 502 is less thanthe value of SPB 504, then the method 700 proceeds to step 715 (FIG.7C). If, however, the value of HXSC 502 is not less than the value ofSPB 504, then the Data Mover 500 determines in step 704 if there is atleast 1 block's worth of available storage in the buffer 205; thisdetermination is based on whether the value of BuffSects 505 is greaterthan or equal to the value of SPB 504. If the value of BuffSects 505 isnot greater than or equal to the value of SPB 504, then the method 700proceeds to step 708 (FIG. 7B).

[0026] If the value of BuffSects 505 is greater than or equal to thevalue of SPB 504, then the Data Mover 500 sends an H_XferBlk 403 signalto the Host Interface 400 requesting that the Host Interface 400transfer a block of data from the host 102 to the buffer 205, asindicated in step 705. After the H_XferBlk 403 signal is sent to theHost Interface 400, a block of data is transferred from the host 102 tothe buffer 205 in step 706 and the Data Mover 500 receives anH_BlkXferred 404 signal from the Host Interface 400 confirming the datatransfer. After the H_BlkXferred 404 signal is received by the DataMover 500 from the Host Interface 400, the values of HXSC 502 andBuffSects 505 are decreased by the value of SPB 504, as indicated instep 707. In addition, if the value of Host_LW_Ptr 511 is equal toEOB_LW_Ptr 516, then the value of Host_LW_Ptr 511 is set equal toSOB_LW_Ptr 515.

[0027] The Data Mover 500 then determines in step 708 (FIG. 7B) if datasectors remain to be transferred to the Storage Medium 104 (FIG. 1);this determination is based on whether the value of DXSC 503 is greaterthan 0. If the value of DXSC 503 is not greater than 0, then the StorageMedium Interface 600 interrupts the microprocessor 201 in step 709 andthe method 700 terminates in step 710. If, however, the value of DXSC503 is greater than 0, then the Data Mover 500 determines in step 711 ifthere is at least one sector of data in the buffer 205; thisdetermination is based on whether the value of BuffSects 505 is lessthan the value of MaxBuffSects 510.

[0028] If the value of BuffSects 505 is less than the value ofMaxBuffSects 510, then the Data Mover 500 sends an SMI_XferSect 508signal to the Storage Medium Interface 600 requesting that the StorageMedium Interface 600 transfer a sector of data from the buffer 205 tothe Storage Medium 104, as indicated in step 712. However, if the valueof BuffSects 505 is not less than the value of MaxBuffSects 510, thenthe method 700 returns to step 703 (FIG. 7A). After the Storage MediumInterface 600 receives an SMI_XferSect 508 signal, the Storage MediumInterface 600 transfers a sector of data from the buffer 205 to theStorage Medium 104, as indicated in step 713, and then sends anSMI_SectXferred 509 signal to the Data Mover 500 confirming thetransfer. After the SMI_SectXferred 509 signal is received by the DataMover 500, the value of DXSC 503 is decreased by 1 and the value ofBuffSects 505 is increased by 1, as indicated in step 714. In addition,if the value of SMI_LW_Ptr 512 is equal to EOB_LW_Ptr 516, then thevalue of SMI_LW_Ptr 512 is set equal to SOB_LW_Ptr 515.

[0029] At step 715 (FIG. 7C), the Data Mover 500 determines if there isa runt block remaining to be transferred. A runt block is an amount ofdata that is less than the unit of data (e.g. block) that the host 102uses in sending or receiving data to the Data Transfer System 200. Thedetermination of whether a runt block remains to be transferred is basedon whether the value of HXSC 502 is greater than 0. If the value of HXSC502 is not greater than 0, then the method 700 proceeds to step 708(FIG. 7B). If, however, the value of HXSC 502 is greater than 0, thenthe Data Mover 500 interrupts the microprocessor 201 in step 716. Afterbeing interrupted, the microprocessor 201 reloads SPB 504 with HXSC 502and Host_LW_PerBlk 506 with a value equal to the value of HXSC 502multiplied by the value of SMI_LW_PerSect 507 (i.e. Host_LW_PerBlk 506is loaded with a value equal to the number of longwords remaining to betransferred). After SPB 504 and Host_LW_PerBlk 506 are reloaded, themethod 700 returns to step 703 so that the runt block may betransferred. After the runt block is transferred, the microprocessor 201reloads SPB 504 and Host_LW_PerBlk 506 with the values that they hadprior to when the microprocessor 201 was interrupted in step 716. In onepossible implementation, the microprocessor is not interrupted in step716; instead, SPB 504 and Host_LW_PerBlk 506 are reloaded prior to therunt block transfer using a specialized circuit without microprocessor201 intervention.

[0030]FIGS. 8A, 8B, and 8C are flow charts depicting a non-limitingexample of a read method that is performed by the Data Transfer System200 (FIG. 2) in accordance with one embodiment of the present invention.In step 801, the Host Interface 400 (FIG. 2) receives a read commandfrom a host 102 (FIG. 1). In response to receiving the read command, theHost Interface 400 interrupts the microprocessor 201 (FIG. 2) which, instep 802, loads the number of sectors per block into SPB 504, thetransfer length in sectors into HXSC 502 and DXSC 503, the number oflongwords in a sector into SMI_LW_PerSect 507, and the number oflongwords in a block into Host_LW_PerBlk 506. In addition, theMicroprocessor 201 sets BuffSects 505 to 0, sets Host_LW_Ptr 511 andSMI_LW_Ptr 512 to SOB_LW_Ptr 515, and then activates the modules HostInterface 400, Data Mover 500, and Storage Medium Interface 600 (FIG.2).

[0031] The Data Mover 500 then determines in step 803 if data sectorsare to be received from the Storage Medium 104 (FIG. 1); thisdetermination is based on whether the value of DXSC 503 is greater than0. If the value of DXSC 503 is not greater than 0, then the method 800proceeds to step 808 (FIG. 8B). If the value of DXSC 503 is greater than0, then the Data Mover 500 determines in step 804 if there is space inthe buffer 205 for receiving a sector of data from the Storage Medium104; this determination is based on whether the value of BuffSects 505is less than the value of MaxBuffSects 510.

[0032] If the value of BuffSects 505 is not less than the value ofMaxBuffSects 510, then the method 800 proceeds to step 808. However, ifthe value of BuffSects 505 is less than the value of MaxBuffSects 510,then the Data Mover 500 sends an SMI_XferSect 508 signal to the StorageMedium Interface 600 requesting that the Storage Medium Interface 600transfer a sector of data from the Storage Medium 104 to the buffer 205,as indicated in step 805. After the Storage Medium Interface 600receives the SMI_XferSect 508 signal, the Storage Medium Interface 600transfers a sector of data from the Storage Medium 104 to the buffer205, as indicated in step 806, and then sends an SMI_SectXferred 509signal to the Data Mover 500 confirming the transfer. After theSMI_SectXferred 509 signal is received by the Data Mover 500 from theStorage Medium Interface 600, the value of DXSC 503 is decreased by 1and the value of BuffSects 505 is increased by 1, as indicated in step807. In addition, if the value of SMI_LW_Ptr 512 is equal to EOB_LW_Ptr516, then the value of SMI_LW_Ptr 512 is set equal to SOB_LW_Ptr 516.

[0033] Subsequently, in step 808 (FIG. 8B), the Data Mover 500determines if the amount of data remaining to be transferred is lessthan a block's worth of data. This determination is based on whether thevalue of HXSC 502 is less than the value of SPB 504. If the value ofHXSC 502 is less than the value of SPB 504, then the method 800 proceedsto step 815 (FIG. 8C). If, however, the value of HXSC 502 is not lessthan the value of SPB 504, then the Data Mover 500 determines in step809 if there is at least 1 block's worth of data in the buffer 205; thisdetermination is based on whether the value of BuffSects 505 is greaterthan or equal to the value of SPB 504. If the value of BuffSects 505 isnot greater than or equal to the value of SPB 504, then the method 800proceeds to step 803 (FIG. 8A). However, if the value of BuffSects 505is greater than or equal to the value of SPB 504, then the Data Mover500 sends an H_XferBlk 403 signal to the Host Interface 400 requestingthat the Host Interface 400 transfer a block of data from the buffer 205to the host 102, as indicated in step 810. After the H_XferBlk 403signal is sent to the Host Interface 400, a block of data is transferredfrom the buffer 205 to the host 102 in step 811 and the Data Mover 500receives an H_BlkXferred 404 signal from the Host Interface 400confirming the data transfer. After the H_BlkXferred 404 signal isreceived by the Data Mover 500 from the Host Interface 400, the valuesof HXSC 502 and BuffSects 505 are decreased by the value of SPB 504, asindicated in step 812. In addition, if the value of Host_LW_Ptr 511 isequal to EOB_LW_Ptr 516, then the value of Host_LW_Ptr 511 is set toSOB_LW_Ptr 515. After the register values are adjusted in step 812, themethod 800 returns to step 803 (FIG. 8A).

[0034] At step 815 (FIG. 8C), the Data Mover 500 determines if there isa runt block remaining to be transferred. The determination of whether arunt block remains to be transferred is based on whether the value ofHXSC 502 is greater than 0. If the Data Mover 500 determines in step 815that the value of HXSC 502 is not greater than 0, then the Data Mover500 interrupts the microprocessor 201 in step 818 and the method 800terminates in step 819. If, however, the value of HXSC 502 is greaterthan 0, then the Data Mover 500 interrupts the microprocessor 201 instep 816. After being interrupted, the microprocessor 201 reloads SPB504 with HXSC 502 and reloads Host_LW_PerBlk 506 with a value equal tothe value of HXSC 502 multiplied by the value of SMI_LW_PerSect 507(i.e., Host_LW_PerBlk 506 is loaded with a value equal to the number oflongwords remaining to be transferred). After SPB 504 and Host_LW_PerBlk506 are reloaded, the method 800 returns to step 808 so that the runtblock may be transferred. After the runt block is transferred, themicroprocessor 201 reloads SPB 504 and Host_LW_PerBlk 506 with thevalues that they had prior to when the microprocessor 201 wasinterrupted in step 816. In one possible implementation, themicroprocessor is not interrupted in step 816. Instead, SPB 504 andHost_LW_PerBlk 506 are reloaded prior to the runt block transfer using aspecialized circuit without microprocessor 201 intervention.

[0035] In an alternative embodiment of the Data Transfer System 200,functions or steps shown in the flow charts depicted in FIGS. 7A, 7B,7C, 8A, 8B, and 8C may be executed out of order from that shown ordiscussed, including substantially concurrently or in reverse order aswould be understood by those reasonably skilled in the art.

[0036] It should be emphasized that the above-described embodiments ofthe present invention are merely possible examples, among others, of theimplementations, setting forth a clear understanding of the principlesof the invention. Many variations and modifications may be made to theabove-described embodiments of the invention without departingsubstantially from the principles of the invention. All suchmodifications and variations are intended to be included herein withinthe scope of the disclosure and present invention and protected by thefollowing claims.

What is claimed is:
 1. A method for transferring data between a hostdevice and a storage medium, comprising: receiving from the host devicea command to transfer data between the host device and a storage medium;storing in a first register a value that is correlated to a number ofsecond data units contained in a first data unit; and storing in asecond register a value for tracking a number of second data units thatare transferred between the host device and a buffer.
 2. The method ofclaim 1, wherein a first data unit is a block of data and a second dataunit is a sector of data.
 3. The method of claim 1, further comprising:storing in a third register a value that is correlated to a number ofthird data units contained in a first data unit.
 4. The method of claim3, wherein a third data unit is a longword of data.
 5. The method ofclaim 3, further comprising: storing in a fourth register a value fortracking a number of fourth data units that are transferred between thehost device and the buffer.
 6. The method of claim 5, wherein a fourthdata unit is a word of data.
 7. The method of claim 5, furthercomprising: storing in a fifth register a value for tracking a number ofsecond data units that are transferred between the storage medium andthe buffer.
 8. The method of claim 7, further comprising: storing in asixth register a value that is correlated to a number of third dataunits contained in a second data unit.
 9. The method of claim 1, whereinthe storage medium comprises non-volatile semiconductor memory.
 10. Themethod of claim 1, further comprising: implementing the method via anapplication specific integrated circuit (ASIC).
 11. The method of claim1, further comprising: storing in a register a value representing astorage capacity of the buffer.
 12. A data transfer system fortransferring data between a host device and a storage medium,comprising: a host interface that receives from the host device acommand to transfer data between the host device and a storage medium; abuffer that temporarily stores data that is transferred between the hostdevice and the storage medium; a first register that stores a value thatis correlated to a number of second data units contained in a first dataunit; and a second register that stores a value for tracking a number ofsecond data units that are transferred between the host device and thebuffer.
 13. The data transfer system of claim 12, further comprising: athird register that stores a value that is correlated to a number ofthird data units contained in a first data unit.
 14. The data transfersystem of claim 13, further comprising: a fourth register that stores avalue for tracking a number of fourth data units that are transferredbetween the host device and the buffer.
 15. The data transfer system ofclaim 14, further comprising: a fifth register that stores a value fortracking a number of second data units that are transferred between thestorage medium and the buffer.
 16. The data transfer system of claim 15,further comprising: a sixth register that stores a value that iscorrelated to a number of third data units contained in a second dataunit.
 17. The data transfer system of claim 12, wherein the datatransfer system is implemented via an application specific integratedcircuit (ASIC).
 18. A method for transferring data between a host deviceand a storage medium, comprising: receiving from the host device acommand to transfer data between the host device and a storage medium;determining a number of second data units contained in a first dataunit; and tracking a number of second data units that are transferredbetween the host device and a buffer.
 19. The method of claim 18,further comprising: determining a number of third data units containedin a first data unit.
 20. The method of claim 19, further comprising:tracking a number of fourth data units that are transferred between thehost device and the buffer.
 21. The method of claim 20, furthercomprising: tracking a number of second data units that are transferredbetween the storage medium and the buffer.
 22. The method of claim 21,further comprising: determining a number of third data units containedin a second data unit.